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How nitrile and vinyl gloves are made
February 23, 2015 By Ammex
Unlike latex gloves, nitrile and vinyl gloves do not come from natural rubber. These gloves come from synthetic materials, but the manufacturing process is not too different from latex glove production.
Here is an overview of how manufacturers create these gloves:
Creating the synthetic materials
The processes for creating the nitrile and vinyl materials is similar.
The nitrile butadiene rubber (NBR) used for nitrile gloves is a copolymer, which is a substance derived through the bonding of different molecules. In the case of NBR, the two parts are butadiene and acrylonitrile, which chemists combine using a process known as copolymerization. These molecules provide specific advantages for the gloves: Acrylonitrile enhances the chemical resistance, while butadiene creates flexibility and tear resistance.
Vinyl gloves come from polyvinyl chloride (PVC) monomers alone. Because chemists use only one species of monomer to create PVC, the material is known as a polymer. Once they have polymerized the substance, the chemists add a chemical called a plasticizer to the PVC. The plasticizer makes the material flexible – otherwise, the PVC would be rigid, as it is when used to form pipe. PVC is inexpensive to create, making it a cost-effective alternative to latex and for applications where glove changes occur frequently.
Chemists combine molecules to create PVC and NBR for disposable gloves.
Producing the gloves
Once the synthetic materials are available, they go to the factory for production. With a few exceptions, this process is mostly the same as the steps for manufacturing latex gloves:
The manufacturing equipment first runs ceramic, hand-shaped formers through water and bleach to clean them and remove any residue from the previous run. The formers then dry to remove all the water. Then, they dip in a mixture of calcium carbonate and calcium nitrate, which helps the synthetic materials coagulate around the formers. Afterward, the formers dry again.
The equipment dips the formers in tanks full of NBR or PVC. The following step involves heating the materials at a high temperature to form the gloves as they dry.
For easier donning, nitrile gloves undergo one of two processes: chlorination or polymer coating. Chlorination involves exposing the gloves to chlorine – as an acid mixture or gas – to make the material harder and more slick. Polymer coating lubricates the glove surface by adding a layer of polymer.
Finally, in what is known as the stripping phase, the gloves are removed from the formers. This is called the stripping phase.
Checking for quality
The last steps of the manufacturing cycle include testing the gloves and shipping them.
The quality control process, which is based on standards from the American Society for Testing and Materials (ATSM) and regulated by the U.S. Food and Drug Administration (FDA), includes the pinhole leak test. While all gloves have some pinholes, this test tells manufacturers whether a glove has enough pinholes to lead to a noticeable leak.
"For easier donning, nitrile gloves undergo chlorination or polymer coating."
After filling the gloves with 1 liter of water, the workers hang them upside down for two minutes to see if the gloves can hold the water. Exam-grade gloves undergo more intensive testing than industrial-grade gloves – the latter is composed of gloves that meet basic quality tests but not the higher standards for exam grading.
These tests adhere to acceptable quality limits (AQLs), which are percentages indicating how many gloves in a batch must fail the test to determine if the entire batch fails.
The final step is for workers to package and pack the gloves. Then, the gloves ship from the manufacturing facilitates in Southeast Asia via ocean freight to their final destinations. With this journey, the gloves have taken the final step from being molecules to effective barrier protection.
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